Recursive-reflective display devices

ABSTRACT

In a retroreflective display device comprising at least a surface-protective layer, information display layer, retroreflective layer and a back-protective layer, on or between these layers radio frequency identification unit or units enclosing radio frequency identification integrated circuit or circuits are disposed, and communication antenna or antennas which are connected to said radio frequency identification integrated circuit or circuits are installed. At the back of the retroreflective layer an illuminator is disposed. The retroreflective layer is retroreflective to the light coming from the front of the sign and is transmissive to the light from the interior of the sign.

TECHNICAL FIELD

This invention relates to retroreflective display devices. Morespecifically, the invention relates to retroreflective display devicesequipped with radio frequency identification units; internallyilluminated retroreflective display devices equipped with radiofrequency identification units; and electroluminescence internallyilluminated retroreflective display devices (hereinafter may be referredto as EL internally illuminated retroreflective display devices).

More specifically, the invention relates to retroreflective displaydevices which exchange information with radio frequency identificationunits via communication antennas and enable, particularly at night,recognition from remote places of location of the display devices of thepresent invention, approach of owners of the devices or viewers thereof,and information given by letters or patterns shown on the displaydevices, by radiating light in accordance with the principle ofretroreflection.

The invention furthermore relates to retroreflective display deviceswhich exchange information with radio frequency identification units viacommunication antennas and enable, particularly at night, recognitionfrom remote places of location of the display devices of the presentinvention, approach of owners of the devices or viewers thereof, andinformation given by letters or patterns indicated on the displaydevices as illuminated by the illuminators provided at the back of theretroreflective layers, and further by radiating light externally toenable recognition of such visual information from remote places inaccordance with the principle of retroreflection, even when the internalilluminators are unable to emit light due to such troubles as powerfailure.

The invention also relates to EL internally illuminated retroreflectivedisplay devices which exchange informations with radio frequencyidentification units via communication antennas and enable, particularlyat night, recognition from remote places of location of the displaydevices of the present invention, approach of the owners of the devicesor viewers thereof, and the information given by letters or patternsindicated on the display devices as illuminated by illuminatorsutilizing EL principle, which are provided at the back of theretroreflective layers, or by radiating light externally to enablerecognition of such visual information from remote places in accordancewith the principle of retroreflection, even when the EL internalilluminators are unable to emit light due to such troubles as powerfailure.

The invention moreover relates to retroreflective display devices inwhich said communication antennas are formed on the reflective surfacesof retroreflective elements.

Those retroreflective display devices according to the present inventionare useful for various commercial signboards and signs for varioustraffic uses such as road signs, construction signs, guide signs, or forvehicle number plates.

BACKGROUND ART

A conventional IC card comprises radio frequency identification unit orunits having built-in integrated circuit or cirnuits, a carrier layer tocarry said identification unit or units, said layer comprising a corelayer and/or an inner layer, and an upper protective layer and a lowerprotective layer for protecting the upper face and the lower face of thecarrier layer, respectively. This laminate exchanges informationsbetween the integrated circuit or circuits and external units throughexternal contact terminals provided on, for example, said upperprotective layer, or a communication antenna which is installed on thecarrier layer.

Such a conventional contact type IC card provided with external contactterminals performs exchange of electronic signal information withexternal read-and-write units (reader/writer), or receives power supply,through the external contact terminals provided, for example, on saidupper protective layer.

A non-contact type IC card which is installed with a communicationantenna (or simply, “antenna”) receives power supply and exchangeselectronic signal information between its integrated circuit module of,e.g., radio frequency identification integrated circuits, and externalreader/writers, through the antenna installed on its carrier layer.

Such non-contact type IC cards are further classified, according to thedistance between the involved integrated circuit enclosed laminate andreader/writers, into close coupling type (within 2 mm), proximitycoupling type (within 10 cm), vicinity coupling type (within 70 cm) anddistance coupling type (more than 70 cm). In general, short waves areused for the close coupling and proximity coupling types which emitradio waves over short ranges; long waves are used for vicinity couplingtype and microwaves, for distance coupling type.

Various methods for forming such a non-contact type IC card with anantenna installed therein have been proposed. As methods for forming theantenna, a method of forming an antenna by partially removing apreviously installed metallic layer by such means as etching, a methodof forming an antenna by partially installing a metallic layer, a methodof forming an antenna by using a conductive ink and a method of formingan antenna by winding a metallic thin wire into a coil are known.

Examples of prior art disclosing these antenna-forming methods includeJP Patent Publication Hei 11(1999)-134461A to Horio and its U.S.counterpart, U.S. Pat. No. 6,160,526; JP Patent Publication Hei10(1998)-320519A to Ikefuji, et al. and its EP counterpart, EP1014301A1; JP Patent Publication Hei 8(1996)-287208A to Orihara, et al.and its US counterpart, U.S. Pat. No. 5,705,852; JP Patent Publication2002-074301A to Okamura, et al. and its US counterpart, U.S. 2002/24475;JP Patent Publication 2000-251047A to Hayashi, et al. and its EPcounterpart, EP 1033778A2; and JP Patent Publication 2000-105810A toHayashi, et al. and its EP counterpart, EP 1039411A1. Disclosures ofthose references can be referred to, for further explanation of theirtechniques.

On the other hand, retroreflective sheetings and retroreflective moldedarticles which are installed with a multiplicity of retroreflectiveunits (hereafter collectively referred to as “retroreflective sheeting”)are used for traffic signs, safety instruments, reflective stickers,commercial signboards and optical-sensor reflectors, particularly forsafety and display instruments in the nighttime, which reflect lighttoward their light sources.

In such retroreflective sheeting, a multiplicity of micro glass beadtype or cube corner prism type retroreflective units are installedinside of the sheeting, which are so designed that entrance light intothe retroreflective units from a light source is reflected once againtoward the light source.

For example, U.S. Pat. No. 4,025,159 to McGrath disclosesretroreflective sheeting using micro glass bead type retroreflectiveunits; U.S. Pat. No. 4,588,258 to Hoopman discloses a retroreflectivesheeting using cube corner prism type retroreflective units; and U.S.Pat. No. 6,083,607 to Mimura discloses a retroreflective sheeting usingcube corner prism type retroreflective units whose retroreflectiveangularity is improved.

Moreover, as a product equipped with retroreflective sheeting and astorage medium, JP Publication Sho 59(1984)-58630A to Tsukane, et al.discloses a product having a retroreflective layer constituted of glassbeads and a magnetic recording layer.

JP Patent Announcement Hei 9(1997)-508983A to Bantli discloses anintegrated retroreflective electronic display device. This patentdiscloses, according to descriptions in its specification, aretroreflective apparatus for visual and electromagnetic datacommunication, said apparatus comprising retroreflective sheeting forretroreflecting entrance light, said sheeting having visual informationsthereon, and comprising a base sheet having a monolayer ofretroreflective microspheres which are embedded in one of its surfacesand a regular light reflecting means which is disposed under saidmicrospheres as spaced therefrom by a transparent material; antennameans for electromagnetic communication; and coupling means for allowingcoupling to said antenna means.

JP Patent Announcement Hei 11(1999)-505050A to Bantli discloses anelectronic license plate having a security identification device.According to disclosures of its specification, said patent discloses anelectronic license plate architecture for use in an electronic vehiclecommunication system in which a plurality of remote traffic managementstations communicate with the electronic license plate, comprising alicense plate portion, including visual identification information andan identification means for storing restricted information, therestricted information including at least one type of vehicleidentification information, and wherein the restricted informationcannot be altered by the remote stations or by the vehicle; informationmeans for storing unrestricted information, wherein the unrestrictedinformation can be altered by at least one of the remote stations or bythe vehicle; communication means, operatively connected to theidentification means and to the information means, for processingcommunications with the remote stations; antenna means for transmittingand receiving the communications with the remote stations; andattachment means fixed to the vehicle for replaceably attaching thelicense plate portion on the vehicle, such that the license plateportion can be replaced without having to replace the information means.

JP Patent Publication Hei 4(1992)-229244A to Martin discloses a methodfor making a retroreflective microprismatic sheeting partially free froma metallic layer, said method comprising partially forming an adhesivelayer on a metallic deposit layer formed on surfaces of retroreflectivemicroprisms and removing a portion of said metallic layer which isunprotected by said adhesive layer. It also states that the partiallyprovided adhesive layer (protective coating material) is desirably apressure-sensitive adhesive which will not be unduly affected during asolvent treating step in later processing. Furthermore, as one of themethods for providing said layer, printing is named.

Furthermore, JP Patent Publication Hei 1(1989)-231004A to Martindiscloses a method for making a retroreflective microprism sheetpartially free from a metallic layer, which comprises forming a metallicdeposit layer on surfaces of retroreflective microprisms, partiallyforming an adhesive layer on said metallic deposit layer and removingthe metallic layer in the areas unprotected by said adhesive layer; anda method for making a retroreflective microprism sheet partially freefrom a metallic layer, which comprises partially installing a coatingmaterial on the retroreflective microprism surfaces, vapor depositing ametal thereon and removing the partially laid coating material.

Methods of removing vapor-deposited layers with laser also have beengenerally practiced.

U.S. Pat. No. 4,200,875 to Galanos discloses a method of forming animage on an exposed lens type retroreflective sheeting in accordancewith a predetermined pattern by a laser method.

Internally illuminated retroreflective display devices are also known.

For example, JP Patent Publication Hei 1 (1989)-298395A to Bradshowdiscloses “an internally illuminated sign comprising an enclosuretransmissive to light on at least one side, designated the front side,and cube corner retroreflective sheeting positioned to reflect lightincident on the front of the sign, wherein the cube cornerretroreflective sheeting:

-   (1) comprises a cover layer having a multiplicity of retroreflective    cube corner elements and a base layer of transparent material bonded    to the cover layer, and-   (2) has areas, where the base layer has been bonded to the cover    layer, which are:-   (a) optically transparent to internal light with an angle of    incidence greater than or equal to zero degrees and less than 90    degrees,-   (b) interspersed among the areas occupied by cube corner elements,    the proportion of such transparent areas to the total sheeting area    and their arrangement relative to each other being fixed to allow    viewing the sign by means of either internal illumination,    retroreflected light, or both.”

JP Patent Publication Hei 2 (1990)-285301A to Benson discloses:

-   -   “an internally illuminated sign comprising a cover which is        transmissive to light on at least one side, designated the front        side, a cover which reflects light incident on the front of the        sign and a retroreflective sheet which is positioned to reflect        light incident on the front of the sign”, which sign uses “a        partially transparent retroreflective article formed by three        intersecting sets of parallel grooves, comprising a base,        prismatic elements having lateral faces intersecting the base at        base edges, and separation surfaces on the base, in which:

-   (a) each set of grooves has a groove side angle that is constant for    that set;

-   (b) the separation surfaces are transparent, are bounded by the base    edges of the lateral faces of the prismatic elements, lie between    the prismatic elements in at least one of the grooves, and have,    taken at any point along any groove in which they lay, curved cross    sections taken across that groove.”

The present inventor, et al. also have disclosed, in Japanese PatentApplication No. 2002-198371, a retroreflective, internally illuminatedsign which comprises an information display section having at least oneflat or curved surface which retroreflects light coming from the frontof said sign and transmits light from the interior of said sign; anilluminator disposed on the back of the information display section; anda housing enclosing and holding these information display section andilluminator, said sign being characterized in that

-   -   the retroreflective unit used in said information display        section is a prismatic retroreflective unit in accordance with        the principle of total internal reflection,    -   a large number of said prismatic retroreflective units are        disposed in closest contact with each other to form a continuous        retroreflective plane, and    -   at least the retroreflective part on the back of said large        number of prismatic retroreflective units has no bonded area        with other layers and has substantially no hermetically sealed        structure.

Whereas, none of the foregoing patents discloses a retroreflectivedisplay device which is characterized by comprising at least a radiofrequency identification unit with built-in integrated circuit orcircuits and an optical retroreflective layer; more specifically aretroreflective display device in which the radio frequencyidentification unit has as enclosed therein radio frequencyidentification-type integrated circuit or circuits and communicationantenna or antennas installed as connected to said radio frequencyidentification-type integrated circuit or circuits; still morespecifically said communication antenna or antennas are formed on thereflective surface of the retroreflective elements.

The inventor of this invention has disclosed in InternationalApplication PCT/JP 02/06070 a retroreflective article with built-inintegrated circuit or circuits which is characterized by comprising atleast an integrated circuit module which encloses integrated circuits,an optical retroreflective element and a carrier layer for theforegoing, which is an improvement of the above-described invention.

The same invention also discloses a retroreflective integratedcircuit-enclosing article in which said integrated circuit moduleencloses radio frequency identification-type integrated circuits and acommunication antenna connected to said radio frequencyidentification-type integrated circuits is installed.

Those known IC cards are subject to such problems that the informationstored in a contact-type IC card cannot be communicated withoutinserting the card into a reader/writer; and also with anon-contact-type IC card, it must approach to a distance near enough toallow identification of radio frequency, advance identification at adistance farther than the identifiable distance being impossible.

Furthermore, in case of a tollage settlement system (hereafter referredto as non-stop automatic toll system) by interactive radio communicationusing a non-contact type IC card on a toll road, there is a problem thatit is usually necessary for each vehicle to install an in-vehicleread-and-write unit to assist the communication with the IC card,because of long distance lying between the IC card and an externalreader/writer (road side communication antenna).

Until a vehicle approaches said reader/writer (road side communicationantenna) near enough to allow the communication with the IC card on thevehicle, therefore, it is difficult for the reader/writer to distinguishvehicles carrying IC cards from those ordinary ones paying toll in cash.In particular, there is a problem at tollgates which concurrently runnon-stop automatic toll system and collect tollage in cash, especiallyin the nighttime, that toll collectors cannot make visualdistinguishment in advance. Because of this problem, automatic tollcollection gates and cash collection gates have to be separated.

Those retroreflective display devices according to the present inventionare used as signs on various commercial signboards and for varioustraffic uses such as road signs, construction signs, guide signs orvehicle number plates, to render the information displayed on thesesigns recognizable also in nighttime, and furthermore to enable stillhigher level information exchange by concurrently reading and writingelectronic information stored in the integrated circuits which areenclosed in these signs with said radio frequency identification units.

In particular, when the technology of the present invention is appliedto vehicle number plates, manufacture information of the vehicle bodiessuch as model, color, date of manufacture and information specific foreach vehicle such as its owner, registration, tax payment, accidentinsurance, checkout and the like, can be comprehensively administered.

Therefore, introduction of the technology of the present inventionenables to promote, solve or control various problems such as recentlyincreasing theft of vehicles or number plates which now is becoming asocial problem, nonpayment of taxes, failure to open accident insurance,negligence to have legal checkout and repair, and the like.

Again, application of the technology to traffic signs enables to supplysuch information as road regulations, construction information, guideinformation and the like to vehicle drivers via in-vehicle readers,besides the drivers' visual recognition of those signs.

DISCLOSURE OF THE INVENTION

As a means to solve those problems, this invention enables checkers'advance recognition of presence of IC cards, before intercommunicationbetween a retroreflective display device of the present invention whichis equipped with radio frequency identification units and areader/writer is carried out. As a means to achieve this aim, a largenumber of retroreflective units are installed in the retroreflectivedisplay device equipped with radio frequency identification units inwhich integrated circuit module or modules are enclosed, so as to enableto reflect light from an external source toward the light source.

More specifically, the invention enables a retroreflective, integratedcircuit-enclosing article which is characterized by comprising at leasta surface-protective layer, information display layer, retroreflectivelayer and back-protective layer and a radio frequency identificationunit with built-in integrated circuit or circuits, to reflect light froman external source toward said light source, by providing a large numberof retroreflective elements on said retroreflective layer.

Visibility of reflection of light by means of retroreflection dropsmarkedly when a viewer is at a position of a large entrance angle.Whereas, in the retroreflective display device of the present invention,an illuminator is provided at the back of the retroreflective layer, andbecause the retroreflective layer is retroreflective to the light comingfrom the front surface of the sign and is transmissive of the lightcoming from the interior of the sign, the device has excellentvisibility also for viewers standing at positions of large observationangles.

Said retroreflective element used in the present invention is composedof cube-corner prismatic retroreflective units (occasionally abbreviatedas “CC units”) or of micro glass bead-type retroreflective units.

As CC units which are retroreflective units used in preferredembodiments of the present invention, at least one type of unitsselected from the group consisting of triangular-pyramidal cube-cornerunits, full cube-type cube-corner units, tent-type cube-corner units andcross-prismatic units can be used. Of these, triangular-pyramidalcube-corner units are preferred, because they easily form a micro sizeretroreflective element and hence enable to form thin products.

These CC units can be used as specular reflection type CC units whichreflect light on their prismatic reflective surfaces, as provided with ametallic thin film layer thereon like micro glass bead-typeretroreflective units; or they may be used as total internal reflectiontype CC units which reflect light on their prismatic reflective surfacesaccording to the principle of total internal reflection, by providing ontheir prismatic backs a layer of a low refractive index, such as of air.The latter total internal reflection type CC units do not requiredeposition of a metallic thin film layer, unlike micro glass bead typeretroreflective units, and hence easily transmit the light from theilluminator internally installed and the appearance of the integratedcircuit enclosed retroreflective products are not darkened by the colorof the metallic thin film layer. Hence, use of such total internalreflection type CC units is advantageous from the standpoint of advancerecognizability.

Moreover, in the case of a non-contact type integrated circuit enclosedretroreflective product, total internal reflection type CCunits arepreferred because they are free from radio frequency noise due to theabsence of metallic thin film layer, unlike said micro glass beadretroreflective units or specular reflection type CC units. Similarsuppression of radio frequency noise can be accomplished when nometallic thin film layer is laid on micro glass bead retroreflectiveunits, but it invites reduction in the retroreflective area and inconsequence, reduction in advance recognizability.

Where a metallic thin film layer is provided on said cube-cornerprismatic retroreflective units, an internally illuminatedretroreflective display device using a retroreflective layer composed ofspecular reflection type cube-corner prisms comprising cube-cornerprisms and a partially provided metallic thin film layer thereon at anareal ratio of less than 80% is preferred, as it allows easytransmission of light from the internally installed illuminator and isless apt to cause radio frequency noise.

Such metallic thin film layer partially provided at an areal ratio ofless than 80% can be formed by a means like etching, to remove themetallic thin film layer, for example, in mesh pattern, to expose theprisms.

Where the areal ratio exceeds 80%, the appearance of the retroreflectivelayer is darkened and percent transmission of the light from internalilluminator drops. Hence such is undesirable.

Said retroreflective element constituting the retroreflective layer mayalso be composed of micro glass bead-type retroreflective units.

As said micro glass bead-type retroreflective units, enclosed lens-typecan be used, which are made by optionally adhering a thin resin filmlayer on micro glass beads preferably having a diameter ranging 30-500μm and a refractive index ranging 1.4-2.5, for adjusting their focaldistance where necessary, and thereafter covering 40-70% of the surfacearea of the micro glass beads with a metallic thin film layer of, forexample, aluminum or silver, by such means as vapor deposition orchemical plating, to increase their retroreflectivity.

A preferred example of retroreflective sheeting using such enclosed lenstype retroreflective units is retroreflective sheeting whoseretrorefletive portion is formed of micro glass bead retrorefletiveunits of 30-500 μm in diameter. The surface of such sheeting is coveredwith a smooth and transparent surface protective layer. Where theretroreflective units have diameters less than 30 μm, diffusion of lightdue to diffraction becomes excessive to undesirably reduceretroreflectivity. Whereas, retroreflective units having diametersexceeding 500 μm render the sheeting thickness too large and areundesirable.

As other micro glass bead-type retroreflective element, encapsulatedlens-type retroreflective units can be used. As such, a retroreflectivesheeting in which the retroreflective units constituting theretroreflective portion are micro glass bead-type retroreflective unitsof 30-500 μm in diameter is preferred. The plastic film constitutingsaid surface protective layer has a smooth and transparent surface.Similar to enclosed lens-type retroreflective sheeting, where thereflective units have a diameter less than 30 μm, diffusion of light dueto diffraction becomes excessive to undesirably reduceretroreflectivity, while the reflective units having a diameterexceeding 500 μm render the thickness of the sheeting too large andundesirably degrade sharpness of formed images.

Again, said micro glass bead-type retroreflective element preferably iscomposed of micro glass bead-type units and a metallic thin film layerpartially laid thereon at an areal ratio of less than 80%, as suchallows easier transmission of the light from the internally installedilluminator and is less apt to cause radio frequency noise.

Where said areal ratio exceeds 80%, appearance of the retroreflectivelayer is darkened and the percent transmission of the light from theinternal illuminator drops, which is undesirable.

It is preferred to use as such retroreflective layer which constitutesthe device of the present invention, a retroreflective integratedcircuit enclosed article as disclosed in International ApplicationPCT/JP02/06070, which is characterized by comprising at least anintegrated circuit enclosed integrated circuit module, opticalretroreflective element and their carrier layer.

Where this article is used, the retroreflective layer encloses thereinat least an electronic recognition device, which may be provided betweenany layers of surface-protective layer, information display layer,retroreflective layer and back-protective layer.

It is also permissible to provide two or more of electronic recognitionunits in which radio frequency identification integrated circuit orcircuits having different carrier frequency characteristics or two ormore antennas of different shapes, said electronic recognition unitsbeing connected by electric circuit or circuits to allow said units tobe stored with common electronic information.

Combined use of two or more of radio frequency identification integratedcircuits having different carrier frequency characteristics enables toutilize, for example, combination of distance coupling type andproximity coupling type reader/writers, by combining differentcommunication distances or communication speeds.

Carrier frequencies decided or under deliberation for ISO rating SC31-18000 are 135 kHz (18000-2), 13.56 kHz (18000-3), 2.45 GkHz(18000-4), 5.85 GHz (18000-5), 860-930 kHz (18000-6) and 433.92 kHz(18000-7). While it is possible to combine two or more of radiofrequency identification integrated circuits having these carrierfrequencies, useful frequencies are not limited to this frequency zone.

Moreover, by combining different communication means using differentmodulation systems, for example, amplitude modulation (AM), amplitudeshift keying (ASK), ON/OFF keying (OOK), bi-phase shift keying (BPSK),phase shift keying (PSK) and frequency shift keying (FSK), improvedcommunication accuracy or secrecy protection of transmitted informationcan be achieved.

Those electronic recognition units connected by electric circuit orcircuits share the electronic information stored in said units incommon, making high level mass information processing possible.

While shape and size of communication antennas useful in the presentinvention are not critical, as examples of the shape coiled or loopantennas can be used.

In particular, for vehicle number plates it is preferred that the entireplates are retroreflective. For example, UK Rating BS AU 145d: 1998Specification for Retroreflecting Number Plates minutely sets rulesconcerning retroreflection rating, and in its FIG. 1 shows the minimumarea which should retroreflect.

According to said FIG. 1 of the UK Rating; the outer periphery of 6 mmin width of the number plate is not required to retroreflect. Hence itis particularly preferred to install a loop antenna in this area,because such meets the UK Rating and enables installation of the maximumsize antenna.

Furthermore, such a communication antenna to enable communicationbetween the radio frequency identification integrated circuit orcircuits and external units can be installed on the carrier layer (corelayer or inner layer), using such materials as thin metallic wire, foilor vapor-deposited metal in the form of mesh, line or loop.

Both of said radio frequency identification integrated circuit orcircuits and communication antenna or antennas are provided betweenthose layers constituting the present invention or inside of saidlayers, and a power supply connector for supplying power from anexternal source or an electromagnetic coupling structure through adielectric for conveying electronic signals are not necessary.Therefore, the antenna or antennas and the integrated radio frequencyidentification integrated circuit or circuits in the present inventionare coupled either directly or through a jumper. As the coupling means,a conductive adhesive, anisotropic bonding sheet, soldering, brazing, orwelding can be used.

To form the antenna to be used for the present invention, a partialinstallation method of partially installing a metallic thin film layer;a partial removal method of partially removing a metallic thin filmlayer, or a mechanical processing method can be used.

As such partial installation method, it is possible to use a methodcomprising setting a mask on the layer on which an antenna is to beinstalled, by such means as printing, masking, or lithography and theninstalling a metallic thin film layer of a desired shape of the antennaby such means as vacuum deposition, sputtering, electroplating orchemical plating.

In the occasion of installing an antenna on retroreflective sheeting bysuch a partial installation method, where the sheeting is micro glassbead type, it is possible to install the antenna and a metallic thinfilm layer simultaneously on an identical layer, through the steps ofembedding micro glass beads, applying, where necessary, a mask on themicro glass beads-embedded side onto which a metallic thin film layer isto be provided via a resin thin film layer, and thereafter depositingaluminum by vacuum vapor deposition method. The antenna thus formedshows retroreflective performance. Also in the case of a prism typeretroreflective sheeting, it is possible to similarly install an antennaand a metallic thin film layer on the same layer at the same time on thereflective surfaces of the prisms.

In the partial removal method, a metallic thin film layer is formed inadvance on the layer on which the antenna is to be installed, by suchmeans as vapor deposition, sputtering, electroplating or chemicalplating, and thereafter said metallic thin film layer is partiallyremoved in a pattern corresponding to the desired shape of the antennaby such means as chemical etching, dry etching, laser illumination or amechanical removal method such as sandblasting.

In the occasion of installing an antenna on the retroreflective sheetingby said partial removal method, a preferred method comprises forming ametallic thin film layer such as of aluminum or the like on an entiresurface of a micro glass bead type retroreflective sheeting or prismaticretroreflective sheeting by a means known per se such as vapordeposition; partially applying an etching solution in a pattern toretain the desired shape of the antenna by a printing method to form theantenna by means of chemical etching; and then neutralizing the etchingsolution and washing it off with water.

As the chemical agent to be used as such chemical etching solution,various types of acids and alkalis can be used. Examples of useful acidsinclude aqueous solutions of hydrochloric acid, nitric acid, sulfuricacid and phosphoric acid, and examples of useful alkalis include aqueoussolutions of sodium hydroxide and potassium hydroxide. Though theconcentration of the chemical etching solution needs to be suitablyselected in accordance with such factors as the kind of the acid oralkali used, thickness of the metallic thin film layer and the etchingrate, generally it can be 5 to 40 wt %.

To perform such chemical etching by a printing method, it is preferableto add various kinds of macromolecular compounds such as polyethyleneglycol, polypropylene glycol, sodium alginate, polyacrylic acid salts,polyvinyl alcohol, and various cellulose derivatives such ashydroxyethylcellulose, carboxylated methylcellulose, and methylcelluloseas viscosity modifiers in order to improve printability. Whereas, thekind and concentration of usable viscosity modifiers can be suitablyselected in accordance with individual printing method and printing rateand therefore, they are subject to no special limitation.

Moreover, it is preferable to add a surface active agent to the chemicaletching solution in order to improve its wettability of, or permeabilityinto, the metallic thin film layer. Kind of useful surface active agentis not particularly restricted. Whereas, those preferred are cationicsurfactants such as amine type, ammonium salt type and pyridinederivatives; anionic surfactants such as sulfated oil, fatty acid salts,sulfated ester oils and alkyl sulfates; and nonionic surfactants such aspartial fatty acid esters of polyhydric alcohols and fatty acid-ethyleneoxide adducts.

Though the printing method is not critical, gravure printing, screenprinting or ink jet method are preferred. Moreover, as other removingmethod, it is possible to use dry etching, laser illumination ormechanical removing method such as sandblasting.

As mechanical processing means, a method of processing a metallic thinplate into an antenna shape by punching or laser processing, orprocessing a thin metallic wire into a loop-form, and mounting soprocessed antenna on the carrier layer can be practiced.

In any of above methods, the metal to be used as the material of themetallic thin film layer or antenna can be suitably selected fromaluminum, aluminum-magnesium alloy, aluminum-manganese alloy, silver,copper, nickel, copper-nickel alloy, brass and phosphor bronze, whichcan be used either singly or as a composite or laminate. Particularly,aluminum and copper are preferable because they excel in radio frequencyreception performance.

A preferred thickness of the metallic thin film layer forming thecommunication antenna is 0.2 to 500 μm. A metallic thin film layerthickness of less than 0.2 μm is undesirable because it is apt to giverise to such problems that the radio frequency reception performance isdeteriorated or the specular reflection characteristic is deterioratedwhen the metallic thin film layer is used as the reflective layer of theretroreflective sheeting. Whereas, a metallic thin film layer thicknessof more than 500 μm is undesirable because it is liable to invite suchproblems that the sheeting thickness becomes excessive, flexibility ofthe sheeting is deteriorated, bendability also is deteriorated, or itcauses deterioration in resolution in the occasion of forming theantenna to make it difficult to obtain a sharp antenna pattern.

Moreover, aluminum is particularly preferable because it shows superioroptical characteristics when it is used as the metallic thin film layerof the retroreflective sheeting. An apparatus suitable for continuousvapor deposition of aluminum thin film layer comprises a vacuum vesselwhich is capable of maintaining a degree of vacuum at around 7×10⁻⁴ to9×10⁻⁴ mmHg, said vacuum vessel accommodating therein a feeder forfeeding an original retroreflective sheeting formed of a base sheet anda surface-protective layer which is laminated on the light entrance sidesurface of said base sheet; a take-up winder for winding up the originalretroreflective sheeting which has been vacuum-deposition treated; and aheating system installed between the feeder and the take-up winder,which is capable of fusing the aluminum in a graphite crucible with anelectric heater. Pure aluminum pellets having a purity of at least 99.99wt % are put in the graphite crucible and it is possible to vacuumdeposit a metallic thin film layer on surfaces of the retroreflectiveunits to a thickness of, e.g., 0.2 to 2 μm with melted and vaporizedaluminum atoms under conditions of, e.g., at an AC voltage of 350 to 360V, electric current of 115 to 120 A and a treatment rate of 30 to 70m/min.

When a communication antenna is provided on the prismatic reflectivesurfaces in the above-described manner, not only the CC units area onwhich the antenna is not mounted, but also all other areas of the CCunits on which the communication antenna is mounted can retroreflectincoming light toward the light source, resulting in excellent advancerecognizability in the nighttime. While conventional communicationantennas can be installed on flat regions only, the communicationantennas which are installed on prismatic reflective surfaces of CCunits or micro glass beads according to the present invention can secureincreased antenna areas due to the uneven surface configuration and,therefore, excel in communication ability.

In the retroreflective layer on which a metallic thin film layer isprovided, said layer on the cube-corner prisms or micro glass bead-typeunits can be divided into electrically insulated lots, not forming acontinuous layer, for the purpose of preventing occurrence of radiofrequency noises from radio waves coming from external units, due to themetallic thin film layer.

The width of the partitions forming the lots, which are not providedwith the metallic thin film layer, may be so narrow as to be visuallyimpossible of perception, so long as it is sufficient to secure electricinsulation. It is preferred, however, that the width of such insulationareas is at least 1 μm. As a means for forming the partitions, etchingmethod as exemplified in the foregoing can be used. The partition areaswith such narrow width do not cause degradation in appearance, thedevice giving uniform retroreflection at night.

Furthermore, with micro glass bead units, it is preferred that themetallic thin film layer provided on the micro glass beads does not forma continuous layer among the micro glass beads, but allows the beads tobe independent of each other as electrically insulated micro glass beadretroreflective units. As a method for obtaining such a micro glass beadretroreflective unit layer, one disclosed in JP Sho 62 (1987)-121043A toBailey, et al. is suitable.

It is also preferred for preventing radio frequency noises, that atleast the metallic thin film layer provided on the cube-corner prisms ormicro glass bead units, which are laid on the area or areas in which thecommunication antenna or antennas are installed, should be removed.

The radio frequency identification integrated circuit module used forthe present invention is composed of memory circuits such as CPU(Central Processing Unit), RAM (Random Access Memory), ROM (Read OnlyMemory), EEPROM (Electronically Erasable Programmable ROM) and the like,and is so designed as to be able to execute processing function, storagefunction and input/output control function.

It also has a built-in non-contact type radio frequency identificationintegrated circuit which is generally referred to as RF-ID (RadioFrequency-Identification IC).

The device furthermore is provided with, as means for exchanginginformation with external units via the communication antenna orantennas, a demodulator for distributing electromotive force induced byradio waves from an external unit, between receiving signal andelectromotive force for the card, binary circuit and besides, modulator,RF amplifier, fitter matching circuit and the like for transmittingsending data.

The surface-protective layer useful for the present invention is notsubject to particular limitation, so long as it is opticallytransparent, transmits radio waves, and is stable to UV rays andmoisture from outside, but such materials as disclosed in InternationalApplication PCT/JP02/06070 filed by the present inventor can be used.

Also for the back-protective layer, one excelling in durability andwhich can prevent infiltration of moisture, UV rays or the like fromoutside can be suitably used.

Those surface-protective layer, information display layer,retroreflective layer, back-protective layer and radio frequencyidentification unit or units provided between the foregoing layers,which constitute a retroreflective device equipped with radio frequencyidentification unit or units according to the present invention, areadhered, connected or integrated by various methods to form a displaydevice of the present invention.

As such methods, those using various adhesives, adhesive sheet,tackifier, tack sheet or the like; heat sealing with heating andpressing; or mechanical fixing, can be applied either singly or insuitable combination. The binding can also be effected by such means asvarious heat-sensitive adhesives, pressure-sensitive adhesives;thermosetting, UV curing or electron beam curing type crosslinkableadhesivers, or thermofusion.

In particular, such various adhesives, adhesive sheet, tackifier or tacksheet are preferably optically transparent and excel in durability. Itis also preferred to add UV absorber, light stabilizer and the like toimprove durability.

Particularly, where present device is to be adhered to alight-transmitting substrate, it is preferable to use apoly(meth)acrylate resin type pressure-sensitive adhesive fromviewpoints of light transmittability and heat resistance. It is alsopreferable to add the same ultraviolet absorber, light stabilizer orantioxidant as those used for the top-protective layer, each at a rateof 0.05 to 5 wt %, for improving weatherability and heat resistance.

An information display layer which is used in the present invention is alayer provided with various literal information, logograms, designs,patterns, photopictures, bar codes and the like. As means for providingsuch, printing methods such as photogravure printing, screen printing,offset printing or ink jet printing; transferring from thermal transferink ribbon; arranging cut-out letters; and the like can be suitablyadopted.

The information display layer may be optically transparent or opaque, orit may be a retroreflective layer.

As an illuminator useful for the present invention, either aback-projector type or side-projector type illuminating device can beused. As the light source useful in each type of illuminating devices,fluorescent lamp, cold-cathode tube, halogen lamp, Xenon lamp, sodiumlamp or LED can be used. Such various light sources are preferablycombined with back-reflective plate or light-guiding plate, to achieveuniform luminance. A back-reflective plate used in the present inventionhas a parabolic cross-sectional configuration focusing on the center ofthe light source, and is most preferably positioned to allow the lightemitted by the light source to enter into the prismatic retroreflectiveunits from their backs at an entrance angle of 0 to 30° to the normalline of the surface constituting the information display section.

Of those useful light sources, LED, in particular, white LED, ispreferred as a low energy-consuming, lowly exothermic and yet highilluminance light source.

A combination of such a light source with a light-guiding plate is anexcellent illumination device for making a thin internally illuminatedsign. While any suitable light-guiding plate can be selected, forexample, a white light-reflective sheet, milk-white, semi-transparentplate, prismatic sheet with linear grooves cut on the surface andprismatic sheet with a surface on which triangular-pyramidal orquadrangular-pyramidal prisms are formed can be used.

Adoption of above-described light-guiding plate or planar luminophor ispreferred because it facilitates entrance of the light emitted by theilluminator used in the retroreflective internally illuminated sign ofthe present invention into the prismatic retroreflective units from theback, at an entrance angle of 0 to 30° to the normal line of the surfaceconstituting the information display section, to effectively intensifythe light transmitting from the back to the front of the sign. Where theentrance angle of the light exceeds 30°, effective transmission of thelight becomes difficult and such is undesirable.

Above-described information display section and illuminator areintegrated by a housing which encloses them. The shape of the housing isnot critical, which can be suitably selected among rectangularparallelepipeds, columns and the like. The material making up said bodyagain is not critical, various materials such as plastics, wood, stoneand the like can be used either singly or in combination. While it ispreferred for the housing to take an hermetically sealed construction toprevent infiltration of water and dust from outside, a constructionallowing discharge of internally generated vapor, heat or externallyinfiltrated water to outside may also be adopted.

Furthermore, accessory devices such as a power source may be installedinside or outside of the housing. The sources include ordinary externalalternating-current power supply, direct-current storage battery andsolar battery. In particular, an illuminator formed of a combination ofsolar battery with low-energy EL light source is preferred from thestandpoint of free maintenance, long life and low energy cost.

Because a planar luminophor using an electroluminescent material is usedas the light source, the invention is suitable for forming thininternally illuminated signs. Moreover, a planar light-emission typeilluminator based on EL principle gives an internally illuminated signshowing very uniform luminance distribution and, therefore, isparticularly preferred.

Adoption of said planar luminophor based on EL principle facilitatesentrance of the light emitted by the illuminator used in theretroreflective internally illuminated sign of the present inventioninto the prismatic retroreflective units from the back, at an entranceangle of 0 to 30° to the normal line of the surface constituting theinformation display section, to effectively intensify the lighttransmitting from the back to the front of the sign. Where the entranceangle of the light exceeds 30°, effective transmission of the lightbecomes difficult and such is undesirable.

Also for the back-protective layer, one excelling in durability, whichcan protect the device of the present invention from infiltration ofmoisture or UV rays from outside can be suitably adopted.

The retroreflective display device of the present invention, which isconstructed as above-described adopts a retroreflective layer carrying alarge number of retroreflective units in a retroreflective displaydevice equipped with radio frequency identification integrated circuitor circuits, as a means to enable viewers to recognize presence ofproducts according to the present invention before mutual communicationof the device with reader/writers become possible, without using anyspecial recognition means and even at night, said reflective layer beingcapable of reflecting light from an external source toward the lightsource. Also by providing an illuminator at the back of saidretroreflective display device, the device can be recognized from a widescope of observation sites.

The retroreflective display device of the present invention excels inimproving advance visual recognizability as aforesaid, and as anotherform of using the article of the present invention, for example, trafficsigns or vehicle number plates can be named. The retroreflective layerused in the article of the present invention, for example, visuallygives recognizable information to a vehicle driver in advance andconcurrently retroreflects a light generated from a light source of areflection type sensor toward a photo receiver located nearby the lightsource, to indicate approach of the display device.

Where a metallic thin film layer is provided on cube-corner prismatic ormicro glass bead units in the retroreflective layer, because the filmdoes not form a continuous layer but is divided into electricallyinsulated lots, occurrence of noise caused by radio waves coming fromexternal sources can be prevented.

Also in the retroreflective display device equipped with two or moreradio frequency identification units having built-in radio frequencyidentification integrated circuit or circuits and communication antennaor antennas, said electronic identification units are connected withelectric circuit or circuits to allow the units to store commonelectronic information, to make high level, mass information processingpossible.

In particular, the retroreflective display device equipped with two ormore radio frequency identification units having built-in radiofrequency identification integrated circuit or circuits andcommunication antenna or antennas, can concurrently conduct proximitycoupling type and distance coupling type identification because theradio frequency identification units have different transmittingfrequencies and hence can conduct high level information processing andinformation management.

The illuminator in combination with electroluminescent light source usedin the present invention makes it possible to provide thin andlight-weight EL internally illuminated retroreflective display device.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is an exploded view showing the construction of a best embodimentof the retroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 2 is an exploded view showing the construction of a best embodimentof the retroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 3 shows appearance of an antenna means to be used with a bestembodiment of the retroreflective display device of the presentinvention, which is provided with radio frequency identification unit orunits.

FIG. 4 shows appearance of an antenna means to be used with a bestembodiment of the retroreflective display device of the presentinvention, which is provided with radio frequency identification unit orunits.

FIG. 5 shows appearance of an antenna means to be used with a bestembodiment of the retroreflective display device of the presentinvention, which is provided with radio frequency identification unit orunits.

FIG. 6 is an exploded view showing the construction of a best embodimentof the retroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 7 is a cross-sectional view of a best embodiment of theretroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 8 is a cross-sectional view of a best embodiment of theretroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 9 is a cross-sectional view of a best embodiment of theretroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 10 is a cross-sectional view of a best embodiment of theretroreflective display device of the present invention, which isprovided with radio frequency identification unit or units.

FIG. 11 is an exploded view showing the construction of a bestembodiment of the internally illuminated retroreflective display deviceof the present invention, which is provided with radio frequencyidentification unit or units.

FIG. 12 is an exploded view showing the construction of a bestembodiment of the internally illuminated retroreflective display deviceof the present invention, which is provided with radio frequencyidentification unit or units.

FIG. 13 is an exploded view showing the construction of a bestembodiment of an EL internally illuminated retroreflective displaydevice of the present invention, which has radio frequencyidentification unit or units.

FIG. 14 is an exploded view showing the construction of a bestembodiment of an EL internally illuminated retroreflective displaydevice of the present invention, which has radio frequencyidentification unit or units.

BEST MODE FOR CAMMING OUT THE INVENTION

First, referring to FIGS. 1-10, best embodiments of the retroreflectivedisplay device of the present invention, each of which is provided withradio frequency identification unit or units are explained.

FIG. 1 shows a preferred embodiment of a radio frequency identificationtype retroreflective vehicle number plate, as an example of theretroreflective display device according to the present invention, whichis provided with one or more radio frequency identification units andone or more communication antennas.

The surface-protective layer 1 is made of 5 mm-thick polymethacrylatesheeting, and on the surface of the retroreflective layer 3 aninformation display layer showing a vehicle number or various logogramsis printed. The radio frequency identification unit 7 is made of a 50μm-thick polyethylene terephthalate sheet, on which a loopedcommunication antenna with an antenna pattern width of 1 mm and a radiofrequency identification integrated circuit having a carrier frequencyof 13.56 MHz are installed as electrically connected with a conductiveadhesive. The back-protective layer 5 and the foregoing layers areintegrated with acrylic adhesives 2 and 4. It is further protected witha polyvinyl chloride cover 6 which prevents infiltration of water ordirt from outside.

As the retroreflective layer, enclosed type retroreflective sheeting,NIKKALITE™ MLG grade manufactured by Nippon Carbide Industries Co., Inc.is used. From its outer edge of 6 mm in width whereon said loop antennais installed, the metallic thin film layer provided on micro glass beadshas been removed by etching using an aqueous sodium hydroxide solution.

FIG. 2 shows another preferred embodiment of a radio frequencyidentification retroreflective vehicle number plate, as another exampleof the retroreflective display device of the present invention, whichhas radio frequency identification unit or units.

In the embodiment illuminated in FIG. 2, a radio frequencyidentification unit 7 is made of a 50 μm-thick polyethyleneterephthalate sheet, on which a coiled communication antenna with anantenna pattern width of 1 mm and a radio frequency identificationintegrated circuit having a carrier frequency of 13.56 MHz are installedas electrically joined with a conductive adhesive.

For the retroreflective layer 3 which is provided with an informationdisplay layer, an internal total reflection type prismaticretroreflective sheeting, NIKKALITE CRYSTAL™ grade # 92801 manufacturedby Nippon Carbide Industries Co., Inc. is used. In this retroreflectivelayer no metallic thin film layer is provided on the retroreflectiveunits, and hence the layer is conveniently free of radio frequencynoises caused by such a metallic thin film layer.

FIGS. 3-5 show preferred embodiments of communication antennas which canbe used for retroreflective display devices according to the presentinvention, which have radio frequency identification units. The areasfilled with diagonal lines in these figures indicate antennas, and theareas painted out black, radio frequency identification integratedcircuits, which are electrically connected with conductive adhesive orthe like via jumpers or the like.

FIG. 3 shows a looped antenna useful for the present invention. FIG. 3also shows the minimum region which must retroreflect, as specified byFIG. 1 of the retroreflection rating in UK Ratings BS AU 145d:1998Specification for Retroreflecting Number Plates. The regions which arenot required to retroreflect are the antenna area as indicated in FIG. 3(of the width within 6 mm) and the two regions enclosed with dottedlines. The metallic thin film layer laid on those retroreflective unitswithin these non-reflective regions can be removed to prevent occurrenceof radio frequency noises.

Moreover, it is preferable also for the most of the reflective region asspecified above, to divide the metallic thin film layer thereover withimperceptibly narrow areas of about 1 μm in width, into electricallyinsulated, separate areas, to prevent radio frequency noises. While thesize or shape of said separating areas are subject to no criticallimitation, they may be such that can divide the retroreflective regioninto 0.5-10 cm square regions. In FIG. 3 the areas are shown ashexagonal meshes, but the separating areas are narrow enough not toallow their easy recognition from its appearance.

FIG. 4 shows a coiled antenna useful for the present invention. With anantenna of this shape, it is preferable either to remove the metallicthin film layer at the location corresponding to that of the antenna inadvance, or to divide it into electrically insulated, separate regionsas above.

An internal total reflection type prismatic retroreflective layer mayalso be sued. This retroreflective layer is preferred because nometallic thin film layer is provided on the retroreflective unitstherein and hence it is free of noises caused by radio frequency.

FIG. 5 shows an ultra-small size loop antenna useful for the presentinvention. Because the area from which the metallic thin film layer isto be removed can be minimized with such a small antenna, thisembodiment also is preferred.

FIG. 6 shows a preferred embodiment of a radio frequency identificationtype traffic sign, as an example of the retroreflective display deviceof the preset invention, which has radio frequency identification unitor units.

A 7.5 mm-thick polymethyl acrylate-made surface-protective layer 1 of 90cm in diameter, and internal total reflection type prismaticretroreflective layer 3 with traffic regulation information printed onthe surface thereof as an information display layer, a radio frequencyidentification unit 7 in which a circular communication loop antenna andradio frequency identification integrated circuit are provided on a 75μm-thick polyethylene terephthalate sheet, and a back-protective layer 5are integrated by adhesive layers 2 and 4.

As the material useful for said back-protective layer, plastics, wood,iron plate or aluminum plate customarily used for traffic signs may benamed. Of these, plastics and wood are preferred.

The traffic sign is mounted on a stationary support 9, with a metalfitting 8.

FIGS. 7-10 show, with cross-sectional views, preferred constructions ofthe retroreflective display devices according to the present invention,which are provided with radio frequency identification units.

FIG. 7 shows an embodiment wherein an enclosed lens type retroreflectivesheeting is used as the retroreflective layer. In FIG. 7, 10 is asurface-protective layer, 12 is an adhesive layer, and 11 is aninformation display layer provided as printed on the retroreflectivelayer. The retroreflective layer is composed of a surface layer 13,printed layer 14 which can also serve as an information display layer,holding layer 16 for retroreflective units, micro glass beads 17,focus-adjusting layer 18, and a metallic, thin film layer 19 forreflecting light. The radio frequency identification unit is composed ofcommunication antennas 22 and a radio frequency identificationintegrated circuit 23, and is adhered between the back-protective layer21 and the retroreflective layer, with an adhesive layer 20.

FIG. 8 shows an embodiment wherein an encapsulated lens typeretroreflective sheeting is used as a retroreflective layer. In FIG. 8,10 is a surface-protective layer, 12 is an adhesive layer, and 14 is aninformation display layer which is provided as printed on theretroreflective layer. The retroreflective layer is composed of asurface layer 13, a binder layer 16 for retroreflective units, microglass beads 17 and a metallic, thin film layer 19 for reflecting light.Said surface layer 13 and the binder layer 16 form a hermetically sealedstructure due to the presence of bonds 29, whereby providing an airlayer 27. The radio frequency identification unit is composed of acarrying layer 24, communication antennas 22 installed thereon and aradio frequency identification integrated circuit 23, and is adheredbetween the back-protective layer 21 and the retroreflective layer, withan adhesive layer 20.

FIG. 9 shows an embodiment wherein an internal total reflection typeprismatic retroreflective sheeting is used as the retroreflective layer.In FIG. 9, 10 is a surface-protective layer, 12 is an adhesive layer,and 11 is an information display layer which is provided on theretroreflective layer by printing. The retroreflective layer is composedof a surface layer 25, a binder layer 28 for retroreflective units, anda micro prismatic layer 26. Said micro prismatic layer 26 and the binderlayer 28 form a hermetically sealed structure to provide an air layer27. The radio frequency identification unit is composed of communicationantennas 22 and a radio frequency identification integrated circuit 23,and is adhered between the back-protective layer 21 and theretroreflective layer, with an adhesive layer 20.

FIG. 10 shows another embodiment wherein an internal totalreflection-type prismatic retroreflective sheeting is used as theretroreflective layer. The surface-protective layer 10 is provided as athinner, more flexible layer than that in the embodiment of FIG. 9, andon its back an information display layer 11 is provided by printing andis bound to the retroreflective layer with an adhesive layer 12.

The microprisms in FIG. 10 are moulded, for example, by compressionmoulding or injection moulding method, as an unflexible, thick layer,which also is provided with bonding portions 29 for forming an air layer27 for effecting internal total reflection, and is whereby bound toradio frequency identification units 22 and 23 mounted on the carryinglayer 24 and to the back-protective layer 21 via adhesive layer 20 toform a hermetically sealed structure.

Next, FIGS. 11 and 12 are referred to, for explaining the bestembodiments of the internally illuminated retroreflective display deviceaccording to the present invention, which encloses radio frequencyidentification unit or units.

FIG. 11 shows a preferred embodiment of the retroreflective traffic signprovided with a back projector type illuminator, as an example of theinternally illuminated retroreflective display device according to thepresent invention, which encloses radio frequency identification unit orunits.

In FIG. 11, 32 is a surface-protective layer with a back-reflectionplate 31 provided on its surface, 33 is a retroreflective layer, 34 is alight-diffusion layer for uniformly dispersing the light from theinside, 39 is a radio frequency identification unit equipped with radiofrequency identification integrated circuit or circuits andcommunication antenna or antennas, 35 is a light source meansconstituting an illuminator, 36 is a back-reflection plate forreflecting the light emitted from the light source means toward thefront face, and 37 is a housing to enclose and support the internallyilluminated retroreflective device.

FIG. 12 shows a preferred embodiment of the retroreflective traffic signprovided with a side-projector type illuminator, as another example ofthe internally illuminated retroreflective display device according tothe present invention, which encloses radio frequency identificationunit or units.

In FIG. 12, 32 is a surface-protective layer with an information displaylayer 31 provided on its surface, 33 is a retroreflective layer, 34 is alight-diffusion layer for uniformly dispersing the light emitted fromthe inside, 39 is a radio frequency identification unit equipped withradio frequency identification integrated circuit or circuits andcommunication antenna or antennas, 35 is a light source meansconstituting an illuminator, 38 is a light-guiding plate for reflectingthe light emitted from the light source means toward the front face, and37 is a housing to close in and support the internally illuminatedretroreflective device.

Now the best embodiments of EL internally illuminated retroreflectivedisplay device having radio frequency identification unit or units ofthe present invention are explained, referring to FIGS. 13 and 14.

FIG. 13 shows a preferred embodiment of a radio frequency identificationtype, internally illuminated retroreflective number plate, as an exampleof the EL internally illuminated retroreflective display device of thepresent invention, which encloses radio frequency identification unit orunits.

In FIG. 13, 41 is a surface-protective layer, 43 is a retroreflectivelayer with an information display layer provided on its surface, 44 is alayer in which radio frequency identification unit or units areinstalled, 45 is a light source means emitting electroluminescence,which is connected to an external source with electric wire 47 and 46 isa rectangular back-protective layer enclosing and supporting theforegoing layers. These layers are laminated with adhesive layers 42.

FIG. 14 shows a preferred embodiment of a radio frequency identificationtype, internally illuminated retroreflective traffic sign, as anotherexample of the EL internally illuminated retroreflective display deviceof the present invention, which encloses radio frequency identificationunit or units.

In FIG. 14, 41 is a surface-protective layer, 43 is a retroreflectivelayer with an information display layer provided on its surface, 44 is alayer in which radio frequency identification unit or units areinstalled, 45 is a light source means emitting electroluminescence,which is connected to an external source with electric wire 47 and 48 isa back-protective layer.

This traffic sign is set up at the edge of a road as a road side trafficsign, with a metal fitting 49 and support 50. The shape of the sign isnot limited to such a road side type, but can be optionally selectedsuch as rectangular road side signs or overhead signs.

1. A retroreflective display device equipped with radio frequencyidentification unit or units, which comprises at least asurface-protective layer, information display layer, retroreflectivelayer and a back-protective layer, and is characterized in that one ormore radio frequency identification units each enclosing radio frequencyidentification integrated circuit are provided on or between theselayers and one or more communication antennas connected to said radiofrequency identification integrated circuits are provided.
 2. Aretroreflective display device equipped with radio frequencyidentification unit or units as described in claim 1, in which saidcommunication antenna or antennas are provided on the back of thereflective surface of a retroreflective element.
 3. A retroreflectivedisplay device as described in claim 1, in which said communicationantenna or antennas are provided on the reflective surface of aretroreflective element.
 4. A retroreflective display device asdescribed in any one of claims 1-3, in which said retroreflectiveelement is constructed of a large number of cube-corner prismaticretroreflective units.
 5. A retroreflective display device as describedin claim 4, in which said cube-corner prismatic retroreflective elementunits are constructed of internal total reflection type cube-cornerprisms.
 6. A retroreflective display device as described in claim 4, inwhich said cube-corner prismatic retroreflective element is constructedof specular reflection type cube-corner prisms which are formed ofcube-corner prisms and a metallic thin film layer provided thereon.
 7. Aretroreflective display device as described in any one of claims 1-3, inwhich said retroreflective element is constructed of a large number ofmicro glass bead-type retroreflective units.
 8. A retroreflectivedisplay device as described in claim 7, in which said micro glassbead-type retroreflective element is formed of the micro glass bead-typeunits and a metallic thin film layer provided thereon.
 9. Aretroreflective display device as described in claim 7, in which saidmicro glass bead-type retroreflective element is formed of the microglass bead-type units and a metallic thin film layer provided thereonvia a thin resin film layer.
 10. A retroreflective display device asdescribed in claim 8, in which said metallic thin film layer provided onsaid cube-corner prisms or micro glass bead units does not form acontinuous layer but is divided into electrically insulated lots.
 11. Aretroreflective display device as described in claim 10, in which saidmetallic thin film layer provided on the micro glass bead units does notform a continuous layer between said micro glass bead units but isdivided to form electrically insulated micro glass bead unitsindependently of each other.
 12. A retroreflective display device asdescribed in claim 10, in which the metallic thin film layer does notform a continuous layer on at least those cube-corner prisms or microglass bead units located in the region or regions on which communicationantenna or antennas are installed, but is divided into electricallyinsulated lots.
 13. A retroreflective display device as described inclaim 12, in which the metallic thin film layer, which is provided on atleast the cube-corner prisms or micro glass bead units which are locatedin the region or regions on which said communication antenna or antennasare installed, is removed.
 14. A retroreflective display device asdescribed in claim 12, in which at least two radio frequencyidentification units each enclosing radio frequency identificationintegrated circuit or circuits with communication antenna or antennasinstalled thereon are provided, said radio frequency identificationunits being connected with electric circuits so that common electronicinformations are stored in said electronic identification units.
 15. Aretroreflective display device as described in claim 14, in which two ormore radio frequency identification units each enclosing radio frequencyidentification integrated circuit or circuits with communicationantennas installed thereon are provided, said radio frequencyidentification units having different propagation frequencies from eachother.
 16. An internally illuminated retroreflective display deviceequipped with radio frequency identification unit or units, which is aretroreflective display device comprising at least a surface-protectivelayer, information display layer, retroreflective layer and aback-protective layer, having one or more radio frequency identificationunits on or between said layers, said radio frequency identificationunit enclosing radio frequency identification integrated circuit orcircuits and having one or more communication antennas installed asconnected to said radio frequency identification integrated circuits;characterized in that it has an internally illuminated sign structurewherein an illuminator is disposed at the back of said retroreflectivelayer, said retroreflective layer being retroreflective to the lightcoming from the front of the sign and transmissive to the light from theinterior of said sign, said structure comprising said surface-protectivelayer, information display layer, retroreflective layer, back-protectivelayer, a radio frequency identification unit or units, an illuminator,and a housing to enclose and support the foregoing.
 17. An internallyilluminated retroreflective display device as described in claim 16, inwhich said communication antenna or antennas are formed at the back ofthe reflective surface of a retroreflective element.
 18. An internallyilluminated retroreflective display device as described in claim 16, inwhich said communication antenna or antennas are formed on thereflective surface of the retroreflective element.
 19. An internallyilluminated retroreflective display device as described in any one ofclaims 16-18, in which the retroreflective element constituting saidretroreflective layer is composed of cube-corner prismaticretroreflective units.
 20. An internally illuminated retroreflectivedisplay device as described in claim 19, in which said cube-cornerprismatic retroreflective units are composed of internal totalreflection type cube-corner prisms.
 21. An internally illuminatedretroreflective device as described in claim 19, in which saidcube-corner prismatic retroreflective units are composed of specularreflection type cube-corner prisms formed of said cube-corner prisms anda metallic thin film layer partially laid thereon with an areal ratio ofless than 80%.
 22. An internally illuminated retroreflective displaydevice as described in claim 21, in which said cube-corner prismaticretroreflective units are at least of one type of cube-corner prismaticretroreflective units selected from the group consisting of triangularpyramidal cube-corner units, full cube-type cube-corner units, tent-typecube-corner units and cross-prismatic units.
 23. An internallyilluminated retroreflective display device as described in any one ofclaims 16-18, in which the retroreflective element constituting theretroreflective layer is composed of micro glass bead-typeretroreflective units.
 24. An internally illuminated retroreflectivedisplay device as described in claim 23, in which said micro glassbead-type retroreflective units are composed of the micro glassbead-type units and a metallic thin film layer partially laid thereon atan areal ratio of less than 80%.
 25. An internally illuminatedretroreflective display device as described in claim 24, in which saidmetallic thin film layer partially laid on the cube-corner prisms ormicro glass bead-type units at an areal ratio of less than 80% does notform a continuous layer but is divided into electrically insulated lots.26. An internally illuminated retroreflective display device asdescribed in claim 24, in which said illuminator used in theretroreflective, internally illuminated sign is either back-projectortype or side-projector type illuminator.
 27. An electroluminescenceinternally illuminated retroreflective display device equipped with aradio frequency identification unit or units, which is a retroreflectivedisplay device comprising at least a surface-protective layer,information display layer, retroreflective layer and a back-protectivelayer, having one or more radio frequency identification units on orbetween said layers, said radio frequency identification unit enclosingradio frequency identification integrated circuit or circuits and havingone or more communication antennas installed as connected to said radiofrequency identification integrated circuits; characterized in that anilluminator according to the principle of electroluminescence isdisposed at the back of the retroreflective layer, said retroreflectivelayer being retroreflective to the light coming from the front of thesign and transmissive to the light from the interior of the sign.
 28. Anelectroluminescence internally illuminated retroreflective displaydevice as described in claim 27, in which said communication antenna orantennas are formed on the back of the reflective surface of theretroreflective element.
 29. An electroluminescence internallyilluminated retroreflective display device as described in claim 27, inwhich said communication antenna or antennas are formed on theretroreflective surface of the retroreflective element.
 30. Anelectroluminescence internally illuminated retroreflective displaydevice as described in any one of claims 27-29, in which theretroreflective element constituting the retroreflective layer iscomposed of cube-corner prismatic retroreflective units.
 31. Anelectroluminescence internally illuminated retroreflective displaydevice as described in claim 30, in which said cube-corner prismaticretroreflective units are composed of internal total reflection typecube-corner prisms.
 32. An electroluminescence internally illuminatedretroreflective display device as described in claim 30, in which saidcube-corner prismatic retroreflective units are composed of specularreflection type cube-corner prisms formed of said cube-corner prisms anda metallic thin film layer partially laid thereon with an areal ratio ofless than 80%.
 33. An electroluminescence internally illuminatedretroreflective display device as described in claim 32, in which saidcube-corner prismatic retroreflective units are at least of one type ofcube-corner prismatic retroreflective units selected from the groupconsisting of triangular pyramidal cube-corner units, full cube-typecube-corner units, tent-type cube-corner units and cross-prismaticunits.
 34. An electroluminescence internally illuminated retroreflectivedisplay device as described in any one of claims 27-29, in which theretroreflective element constituting the retroreflective layer iscomposed of micro glass bead-type retroreflective units.
 35. Anelectroluminescence internally illuminated retroreflective displaydevice as described in claim 34, in which said micro glass bead-typeretroreflective units are composed of the micro glass bead-type unitsand a metallic thin film layer partially laid thereon at an areal ratioof less than 80%.
 36. An electroluminescence internally illuminatedretroreflective display device as described in claim 35, in which saidmetallic thin film layer partially laid on the cube-corner prisms ormicro glass bead-type units at an areal ratio of less than 80% does notform a continuous layer but is divided into electrically insulated lots.